flashrom/flashrom.c

/*
 * This file is part of the flashrom project.
 *
 * Copyright (C) 2000 Silicon Integrated System Corporation
 * Copyright (C) 2004 Tyan Corp <yhlu@tyan.com>
 * Copyright (C) 2005-2008 coresystems GmbH
 * Copyright (C) 2008,2009 Carl-Daniel Hailfinger
 * Copyright (C) 2016 secunet Security Networks AG
 * (Written by Nico Huber <nico.huber@secunet.com> for secunet)
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <stdbool.h>
#include <stdio.h>
#include <sys/types.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <ctype.h>

#include "flash.h"
#include "flashchips.h"
#include "programmer.h"
#include "hwaccess_physmap.h"
#include "chipdrivers.h"

const char flashrom_version[] = FLASHROM_VERSION;

static const struct programmer_entry *programmer = NULL;

/*
 * Programmers supporting multiple buses can have differing size limits on
 * each bus. Store the limits for each bus in a common struct.
 */
struct decode_sizes max_rom_decode;

/* If nonzero, used as the start address of bottom-aligned flash. */
unsigned long flashbase;

/* Is writing allowed with this programmer? */
bool programmer_may_write;

#define SHUTDOWN_MAXFN 32
static int shutdown_fn_count = 0;
/** @private */
static struct shutdown_func_data {
	int (*func) (void *data);
	void *data;
} shutdown_fn[SHUTDOWN_MAXFN];
/* Initialize to 0 to make sure nobody registers a shutdown function before
 * programmer init.
 */
static bool may_register_shutdown = false;

/* Did we change something or was every erase/write skipped (if any)? */
static bool all_skipped = true;

struct programmer_cfg {
	char *params;
};

/* Register a function to be executed on programmer shutdown.
 * The advantage over atexit() is that you can supply a void pointer which will
 * be used as parameter to the registered function upon programmer shutdown.
 * This pointer can point to arbitrary data used by said function, e.g. undo
 * information for GPIO settings etc. If unneeded, set data=NULL.
 * Please note that the first (void *data) belongs to the function signature of
 * the function passed as first parameter.
 */
int register_shutdown(int (*function) (void *data), void *data)
{
	if (shutdown_fn_count >= SHUTDOWN_MAXFN) {
		msg_perr("Tried to register more than %i shutdown functions.\n",
			 SHUTDOWN_MAXFN);
		return 1;
	}
	if (!may_register_shutdown) {
		msg_perr("Tried to register a shutdown function before "
			 "programmer init.\n");
		return 1;
	}
	shutdown_fn[shutdown_fn_count].func = function;
	shutdown_fn[shutdown_fn_count].data = data;
	shutdown_fn_count++;

	return 0;
}

int register_chip_restore(chip_restore_fn_cb_t func,
			  struct flashctx *flash, uint8_t status)
{
	if (flash->chip_restore_fn_count >= MAX_CHIP_RESTORE_FUNCTIONS) {
		msg_perr("Tried to register more than %i chip restore"
		         " functions.\n", MAX_CHIP_RESTORE_FUNCTIONS);
		return 1;
	}
	flash->chip_restore_fn[flash->chip_restore_fn_count].func = func;
	flash->chip_restore_fn[flash->chip_restore_fn_count].status = status;
	flash->chip_restore_fn_count++;

	return 0;
}

static int deregister_chip_restore(struct flashctx *flash)
{
	int rc = 0;

	while (flash->chip_restore_fn_count > 0) {
		int i = --flash->chip_restore_fn_count;
		rc |= flash->chip_restore_fn[i].func(
			flash, flash->chip_restore_fn[i].status);
	}

	return rc;
}

int programmer_init(const struct programmer_entry *prog, const char *param)
{
	int ret;

	if (prog == NULL) {
		msg_perr("Invalid programmer specified!\n");
		return -1;
	}
	programmer = prog;
	/* Initialize all programmer specific data. */
	/* Default to unlimited decode sizes. */
	max_rom_decode = (const struct decode_sizes) {
		.parallel	= 0xffffffff,
		.lpc		= 0xffffffff,
		.fwh		= 0xffffffff,
		.spi		= 0xffffffff,
	};
	/* Default to top aligned flash at 4 GB. */
	flashbase = 0;
	/* Registering shutdown functions is now allowed. */
	may_register_shutdown = true;
	/* Default to allowing writes. Broken programmers set this to 0. */
	programmer_may_write = true;

	struct programmer_cfg cfg;

	if (param) {
		cfg.params = strdup(param);
		if (!cfg.params) {
			msg_perr("Out of memory!\n");
			return ERROR_FLASHROM_FATAL;
		}
	} else {
		cfg.params = NULL;
	}

	msg_pdbg("Initializing %s programmer\n", prog->name);
	ret = prog->init(&cfg);
	if (cfg.params && strlen(cfg.params)) {
		if (ret != 0) {
			/* It is quite possible that any unhandled programmer parameter would have been valid,
			 * but an error in actual programmer init happened before the parameter was evaluated.
			 */
			msg_pwarn("Unhandled programmer parameters (possibly due to another failure): %s\n",
				  cfg.params);
		} else {
			/* Actual programmer init was successful, but the user specified an invalid or unusable
			 * (for the current programmer configuration) parameter.
			 */
			msg_perr("Unhandled programmer parameters: %s\n", cfg.params);
			msg_perr("Aborting.\n");
			ret = ERROR_FLASHROM_FATAL;
		}
	}
	free(cfg.params);
	return ret;
}

/** Calls registered shutdown functions and resets internal programmer-related variables.
 * Calling it is safe even without previous initialization, but further interactions with programmer support
 * require a call to programmer_init() (afterwards).
 *
 * @return The OR-ed result values of all shutdown functions (i.e. 0 on success). */
int programmer_shutdown(void)
{
	int ret = 0;

	/* Registering shutdown functions is no longer allowed. */
	may_register_shutdown = false;
	while (shutdown_fn_count > 0) {
		int i = --shutdown_fn_count;
		ret |= shutdown_fn[i].func(shutdown_fn[i].data);
	}
	registered_master_count = 0;

	return ret;
}

void *master_map_flash_region(const struct registered_master *mst,
			      const char *descr, uintptr_t phys_addr,
			      size_t len)
{
	/* Check the bus master for a specialized map_flash_region; default to
	 * fallback if it does not specialize it
	 */
	void *(*map_flash_region) (const char *descr, uintptr_t phys_addr, size_t len) = NULL;
	if (mst->buses_supported & BUS_SPI)
		map_flash_region = mst->spi.map_flash_region;
	else if (mst->buses_supported & BUS_NONSPI)
		map_flash_region = mst->par.map_flash_region;

	/* A result of NULL causes mapped addresses to be chip physical
	 * addresses, assuming only a single region is mapped (the entire flash
	 * space).  Chips with a second region (like a register map) require a
	 * real memory mapping to distinguish the different ranges.  Those chips
	 * are FWH/LPC, so the bus master provides a real mapping.
	 */
	void *ret = NULL;
	if (map_flash_region)
		ret = map_flash_region(descr, phys_addr, len);
	msg_gspew("%s: mapping %s from 0x%0*" PRIxPTR " to 0x%0*" PRIxPTR "\n",
		__func__, descr, PRIxPTR_WIDTH, phys_addr, PRIxPTR_WIDTH, (uintptr_t) ret);
	return ret;
}

void master_unmap_flash_region(const struct registered_master *mst,
			       void *virt_addr, size_t len)
{
	void (*unmap_flash_region) (void *virt_addr, size_t len) = NULL;
	if (mst->buses_supported & BUS_SPI)
		unmap_flash_region = mst->spi.unmap_flash_region;
	else if (mst->buses_supported & BUS_NONSPI)
		unmap_flash_region = mst->par.unmap_flash_region;

	if (unmap_flash_region)
		unmap_flash_region(virt_addr, len);
	msg_gspew("%s: unmapped 0x%0*" PRIxPTR "\n", __func__, PRIxPTR_WIDTH, (uintptr_t)virt_addr);
}

static bool master_uses_physmap(const struct registered_master *mst)
{
#if CONFIG_INTERNAL == 1
	if (mst->buses_supported & BUS_SPI)
		return mst->spi.map_flash_region == physmap;
	else if (mst->buses_supported & BUS_NONSPI)
		return mst->par.map_flash_region == physmap;
#endif
	return false;
}

void programmer_delay(const struct flashctx *flash, unsigned int usecs)
{
	if (usecs == 0)
		return;

	/**
	 * Drivers should either use default_delay() directly or their
	 * own custom delay. Only core flashrom logic calls programmer_delay()
	 * which should always have a valid flash context. A NULL context
	 * more than likely indicates a layering violation or BUG however
	 * for now dispatch a default_delay() as a safe default for the NULL
	 * base case.
	 */
	if (!flash) {
		msg_perr("%s called with NULL flash context. "
			 "Please report a bug at flashrom@flashrom.org\n",
			 __func__);
		return default_delay(usecs);
	}

	if (flash->mst->buses_supported & BUS_SPI) {
		if (flash->mst->spi.delay)
			return flash->mst->spi.delay(flash, usecs);
	} else if (flash->mst->buses_supported & BUS_PARALLEL) {
		if (flash->mst->par.delay)
			return flash->mst->par.delay(flash, usecs);
	}

	return default_delay(usecs);
}

int read_memmapped(struct flashctx *flash, uint8_t *buf, unsigned int start,
		   int unsigned len)
{
	chip_readn(flash, buf, flash->virtual_memory + start, len);

	return 0;
}

/* This is a somewhat hacked function similar in some ways to strtok().
 * It will look for needle with a subsequent '=' in haystack, return a copy of
 * needle and remove everything from the first occurrence of needle to the next
 * delimiter from haystack.
 */
static char *extract_param(char *const *haystack, const char *needle, const char *delim)
{
	char *param_pos, *opt_pos, *rest;
	char *opt = NULL;
	int optlen;
	int needlelen;

	needlelen = strlen(needle);
	if (!needlelen) {
		msg_gerr("%s: empty needle! Please report a bug at "
			 "flashrom@flashrom.org\n", __func__);
		return NULL;
	}
	/* No programmer parameters given. */
	if (*haystack == NULL)
		return NULL;
	param_pos = strstr(*haystack, needle);
	do {
		if (!param_pos)
			return NULL;
		/* Needle followed by '='? */
		if (param_pos[needlelen] == '=') {
			/* Beginning of the string? */
			if (param_pos == *haystack)
				break;
			/* After a delimiter? */
			if (strchr(delim, *(param_pos - 1)))
				break;
		}
		/* Continue searching. */
		param_pos++;
		param_pos = strstr(param_pos, needle);
	} while (1);

	if (param_pos) {
		/* Get the string after needle and '='. */
		opt_pos = param_pos + needlelen + 1;
		optlen = strcspn(opt_pos, delim);
		/* Return an empty string if the parameter was empty. */
		opt = malloc(optlen + 1);
		if (!opt) {
			msg_gerr("Out of memory!\n");
			return NULL;
		}
		strncpy(opt, opt_pos, optlen);
		opt[optlen] = '\0';
		rest = opt_pos + optlen;
		/* Skip all delimiters after the current parameter. */
		rest += strspn(rest, delim);
		memmove(param_pos, rest, strlen(rest) + 1);
		/* We could shrink haystack, but the effort is not worth it. */
	}

	return opt;
}

char *extract_programmer_param_str(const struct programmer_cfg *cfg, const char *param_name)
{
	return extract_param(&cfg->params, param_name, ",");
}

/* special unit-test hook */
erasefunc_t *g_test_erase_injector;

static erasefunc_t *lookup_erase_func_ptr(const struct block_eraser *const eraser)
{
	switch (eraser->block_erase) {
		case SPI_BLOCK_ERASE_EMULATION: return &spi_block_erase_emulation;
		case SPI_BLOCK_ERASE_20: return &spi_block_erase_20;
		case SPI_BLOCK_ERASE_21: return &spi_block_erase_21;
		case SPI_BLOCK_ERASE_40: return NULL; // FIXME unhandled &spi_block_erase_40;
		case SPI_BLOCK_ERASE_50: return &spi_block_erase_50;
		case SPI_BLOCK_ERASE_52: return &spi_block_erase_52;
		case SPI_BLOCK_ERASE_53: return &spi_block_erase_53;
		case SPI_BLOCK_ERASE_5C: return &spi_block_erase_5c;
		case SPI_BLOCK_ERASE_60: return &spi_block_erase_60;
		case SPI_BLOCK_ERASE_62: return &spi_block_erase_62;
		case SPI_BLOCK_ERASE_81: return &spi_block_erase_81;
		case SPI_BLOCK_ERASE_C4: return &spi_block_erase_c4;
		case SPI_BLOCK_ERASE_C7: return &spi_block_erase_c7;
		case SPI_BLOCK_ERASE_D7: return &spi_block_erase_d7;
		case SPI_BLOCK_ERASE_D8: return &spi_block_erase_d8;
		case SPI_BLOCK_ERASE_DB: return &spi_block_erase_db;
		case SPI_BLOCK_ERASE_DC: return &spi_block_erase_dc;
		case S25FL_BLOCK_ERASE: return &s25fl_block_erase;
		case S25FS_BLOCK_ERASE_D8: return &s25fs_block_erase_d8;
		case JEDEC_SECTOR_ERASE: return &erase_sector_jedec; // TODO rename to &jedec_sector_erase;
		case JEDEC_BLOCK_ERASE: return &erase_block_jedec; // TODO rename to &jedec_block_erase;
		case JEDEC_CHIP_BLOCK_ERASE: return &erase_chip_block_jedec; // TODO rename to &jedec_chip_block_erase;
		case OPAQUE_ERASE: return &erase_opaque; // TODO rename to &opqaue_erase;
		case SPI_ERASE_AT45CS_SECTOR: return &spi_erase_at45cs_sector;
		case SPI_ERASE_AT45DB_BLOCK: return &spi_erase_at45db_block;
		case SPI_ERASE_AT45DB_CHIP: return &spi_erase_at45db_chip;
		case SPI_ERASE_AT45DB_PAGE: return &spi_erase_at45db_page;
		case SPI_ERASE_AT45DB_SECTOR: return &spi_erase_at45db_sector;
		case ERASE_CHIP_28SF040: return &erase_chip_28sf040;
		case ERASE_SECTOR_28SF040: return &erase_sector_28sf040;
		case ERASE_BLOCK_82802AB: return &erase_block_82802ab;
		case ERASE_SECTOR_49LFXXXC: return &erase_sector_49lfxxxc;
		case STM50_SECTOR_ERASE: return &erase_sector_stm50; // TODO rename to &stm50_sector_erase;
		case EDI_CHIP_BLOCK_ERASE: return &edi_chip_block_erase;
		case TEST_ERASE_INJECTOR: return g_test_erase_injector;
	/* default: total function, 0 indicates no erase function set.
	 * We explicitly do not want a default catch-all case in the switch
	 * to ensure unhandled enum's are compiler warnings.
	 */
		case NO_BLOCK_ERASE_FUNC: return NULL;
	};

	return NULL;
}

static int check_block_eraser(const struct flashctx *flash, int k, int log)
{
	struct block_eraser eraser = flash->chip->block_erasers[k];

	if (eraser.block_erase == NO_BLOCK_ERASE_FUNC && !eraser.eraseblocks[0].count) {
		if (log)
			msg_cdbg("not defined. ");
		return 1;
	}
	if (eraser.block_erase == NO_BLOCK_ERASE_FUNC && eraser.eraseblocks[0].count) {
		if (log)
			msg_cdbg("eraseblock layout is known, but matching "
				 "block erase function is not implemented. ");
		return 1;
	}
	if (eraser.block_erase != NO_BLOCK_ERASE_FUNC && !eraser.eraseblocks[0].count) {
		if (log)
			msg_cdbg("block erase function found, but "
				 "eraseblock layout is not defined. ");
		return 1;
	}
	// TODO: Once erase functions are annotated with allowed buses, check that as well.
	return 0;
}

/* Returns the number of well-defined erasers for a chip. */
static unsigned int count_usable_erasers(const struct flashctx *flash)
{
	unsigned int usable_erasefunctions = 0;
	int k;
	for (k = 0; k < NUM_ERASEFUNCTIONS; k++) {
		if (!check_block_eraser(flash, k, 0))
			usable_erasefunctions++;
	}
	return usable_erasefunctions;
}

static int compare_range(const uint8_t *wantbuf, const uint8_t *havebuf, unsigned int start, unsigned int len)
{
	int ret = 0, failcount = 0;
	unsigned int i;
	for (i = 0; i < len; i++) {
		if (wantbuf[i] != havebuf[i]) {
			/* Only print the first failure. */
			if (!failcount++)
				msg_cerr("FAILED at 0x%08x! Expected=0x%02x, Found=0x%02x,",
					 start + i, wantbuf[i], havebuf[i]);
		}
	}
	if (failcount) {
		msg_cerr(" failed byte count from 0x%08x-0x%08x: 0x%x\n",
			 start, start + len - 1, failcount);
		ret = -1;
	}
	return ret;
}

/* start is an offset to the base address of the flash chip */
static int check_erased_range(struct flashctx *flash, unsigned int start, unsigned int len)
{
	int ret;
	const uint8_t erased_value = ERASED_VALUE(flash);

	uint8_t *cmpbuf = malloc(len);
	if (!cmpbuf) {
		msg_gerr("Out of memory!\n");
		return -1;
	}
	memset(cmpbuf, erased_value, len);
	ret = verify_range(flash, cmpbuf, start, len);

	free(cmpbuf);
	return ret;
}

/* special unit-test hook */
read_func_t *g_test_read_injector;

static read_func_t *lookup_read_func_ptr(const struct flashchip *chip)
{
	switch (chip->read) {
		case SPI_CHIP_READ: return &spi_chip_read;
		case READ_OPAQUE: return &read_opaque;
		case READ_MEMMAPPED: return &read_memmapped;
		case EDI_CHIP_READ: return &edi_chip_read;
		case SPI_READ_AT45DB: return spi_read_at45db;
		case SPI_READ_AT45DB_E8: return spi_read_at45db_e8;
		case TEST_READ_INJECTOR: return g_test_read_injector;
	/* default: total function, 0 indicates no read function set.
	 * We explicitly do not want a default catch-all case in the switch
	 * to ensure unhandled enum's are compiler warnings.
	 */
		case NO_READ_FUNC: return NULL;
	};

	return NULL;
}

int read_flash(struct flashctx *flash, uint8_t *buf, unsigned int start, unsigned int len)
{
	read_func_t *read_func = lookup_read_func_ptr(flash->chip);
	return read_func(flash, buf, start, len);
}

/*
 * @cmpbuf	buffer to compare against, cmpbuf[0] is expected to match the
 *		flash content at location start
 * @start	offset to the base address of the flash chip
 * @len		length of the verified area
 * @return	0 for success, -1 for failure
 */
int verify_range(struct flashctx *flash, const uint8_t *cmpbuf, unsigned int start, unsigned int len)
{
	if (!len)
		return -1;

	if (start + len > flash->chip->total_size * 1024) {
		msg_gerr("Error: %s called with start 0x%x + len 0x%x >"
			" total_size 0x%x\n", __func__, start, len,
			flash->chip->total_size * 1024);
		return -1;
	}

	uint8_t *readbuf = malloc(len);
	if (!readbuf) {
		msg_gerr("Out of memory!\n");
		return -1;
	}

	int ret = read_flash(flash, readbuf, start, len);
	if (ret) {
		msg_gerr("Verification impossible because read failed "
			 "at 0x%x (len 0x%x)\n", start, len);
		ret = -1;
		goto out_free;
	}

	ret = compare_range(cmpbuf, readbuf, start, len);
out_free:
	free(readbuf);
	return ret;
}

/* Helper function for need_erase() that focuses on granularities of gran bytes. */
static int need_erase_gran_bytes(const uint8_t *have, const uint8_t *want, unsigned int len,
                                 unsigned int gran, const uint8_t erased_value)
{
	unsigned int i, j, limit;
	for (j = 0; j < len / gran; j++) {
		limit = min (gran, len - j * gran);
		/* Are 'have' and 'want' identical? */
		if (!memcmp(have + j * gran, want + j * gran, limit))
			continue;
		/* have needs to be in erased state. */
		for (i = 0; i < limit; i++)
			if (have[j * gran + i] != erased_value)
				return 1;
	}
	return 0;
}

/*
 * Check if the buffer @have can be programmed to the content of @want without
 * erasing. This is only possible if all chunks of size @gran are either kept
 * as-is or changed from an all-ones state to any other state.
 *
 * Warning: This function assumes that @have and @want point to naturally
 * aligned regions.
 *
 * @have        buffer with current content
 * @want        buffer with desired content
 * @len		length of the checked area
 * @gran	write granularity (enum, not count)
 * @return      0 if no erase is needed, 1 otherwise
 */
static int need_erase(const uint8_t *have, const uint8_t *want, unsigned int len,
               enum write_granularity gran, const uint8_t erased_value)
{
	int result = 0;
	unsigned int i;

	switch (gran) {
	case write_gran_1bit:
		for (i = 0; i < len; i++)
			if ((have[i] & want[i]) != want[i]) {
				result = 1;
				break;
			}
		break;
	case write_gran_1byte:
		for (i = 0; i < len; i++)
			if ((have[i] != want[i]) && (have[i] != erased_value)) {
				result = 1;
				break;
			}
		break;
	case write_gran_128bytes:
		result = need_erase_gran_bytes(have, want, len, 128, erased_value);
		break;
	case write_gran_256bytes:
		result = need_erase_gran_bytes(have, want, len, 256, erased_value);
		break;
	case write_gran_264bytes:
		result = need_erase_gran_bytes(have, want, len, 264, erased_value);
		break;
	case write_gran_512bytes:
		result = need_erase_gran_bytes(have, want, len, 512, erased_value);
		break;
	case write_gran_528bytes:
		result = need_erase_gran_bytes(have, want, len, 528, erased_value);
		break;
	case write_gran_1024bytes:
		result = need_erase_gran_bytes(have, want, len, 1024, erased_value);
		break;
	case write_gran_1056bytes:
		result = need_erase_gran_bytes(have, want, len, 1056, erased_value);
		break;
	case write_gran_1byte_implicit_erase:
		/* Do not erase, handle content changes from anything->0xff by writing 0xff. */
		result = 0;
		break;
	default:
		msg_cerr("%s: Unsupported granularity! Please report a bug at "
			 "flashrom@flashrom.org\n", __func__);
	}
	return result;
}

/**
 * Check if the buffer @have needs to be programmed to get the content of @want.
 * If yes, return 1 and fill in first_start with the start address of the
 * write operation and first_len with the length of the first to-be-written
 * chunk. If not, return 0 and leave first_start and first_len undefined.
 *
 * Warning: This function assumes that @have and @want point to naturally
 * aligned regions.
 *
 * @have	buffer with current content
 * @want	buffer with desired content
 * @len		length of the checked area
 * @gran	write granularity (enum, not count)
 * @first_start	offset of the first byte which needs to be written (passed in
 *		value is increased by the offset of the first needed write
 *		relative to have/want or unchanged if no write is needed)
 * @return	length of the first contiguous area which needs to be written
 *		0 if no write is needed
 *
 * FIXME: This function needs a parameter which tells it about coalescing
 * in relation to the max write length of the programmer and the max write
 * length of the chip.
 */
static unsigned int get_next_write(const uint8_t *have, const uint8_t *want, unsigned int len,
			  unsigned int *first_start,
			  enum write_granularity gran)
{
	bool need_write = false;
	unsigned int rel_start = 0, first_len = 0;
	unsigned int i, limit, stride;

	switch (gran) {
	case write_gran_1bit:
	case write_gran_1byte:
	case write_gran_1byte_implicit_erase:
		stride = 1;
		break;
	case write_gran_128bytes:
		stride = 128;
		break;
	case write_gran_256bytes:
		stride = 256;
		break;
	case write_gran_264bytes:
		stride = 264;
		break;
	case write_gran_512bytes:
		stride = 512;
		break;
	case write_gran_528bytes:
		stride = 528;
		break;
	case write_gran_1024bytes:
		stride = 1024;
		break;
	case write_gran_1056bytes:
		stride = 1056;
		break;
	default:
		msg_cerr("%s: Unsupported granularity! Please report a bug at "
			 "flashrom@flashrom.org\n", __func__);
		/* Claim that no write was needed. A write with unknown
		 * granularity is too dangerous to try.
		 */
		return 0;
	}
	for (i = 0; i < len / stride; i++) {
		limit = min(stride, len - i * stride);
		/* Are 'have' and 'want' identical? */
		if (memcmp(have + i * stride, want + i * stride, limit)) {
			if (!need_write) {
				/* First location where have and want differ. */
				need_write = true;
				rel_start = i * stride;
			}
		} else {
			if (need_write) {
				/* First location where have and want
				 * do not differ anymore.
				 */
				break;
			}
		}
	}
	if (need_write)
		first_len = min(i * stride - rel_start, len);
	*first_start += rel_start;
	return first_len;
}

void unmap_flash(struct flashctx *flash)
{
	if (flash->virtual_registers != (chipaddr)ERROR_PTR) {
		master_unmap_flash_region(flash->mst, (void *)flash->virtual_registers, flash->chip->total_size * 1024);
		flash->physical_registers = 0;
		flash->virtual_registers = (chipaddr)ERROR_PTR;
	}

	if (flash->virtual_memory != (chipaddr)ERROR_PTR) {
		master_unmap_flash_region(flash->mst, (void *)flash->virtual_memory, flash->chip->total_size * 1024);
		flash->physical_memory = 0;
		flash->virtual_memory = (chipaddr)ERROR_PTR;
	}
}

int map_flash(struct flashctx *flash)
{
	/* Init pointers to the fail-safe state to distinguish them later from legit values. */
	flash->virtual_memory = (chipaddr)ERROR_PTR;
	flash->virtual_registers = (chipaddr)ERROR_PTR;

	/* FIXME: This avoids mapping (and unmapping) of flash chip definitions with size 0.
	 * These are used for various probing-related hacks that would not map successfully anyway and should be
	 * removed ASAP. */
	if (flash->chip->total_size == 0)
		return 0;

	const chipsize_t size = flash->chip->total_size * 1024;
	uintptr_t base = flashbase ? flashbase : (0xffffffff - size + 1);
	void *addr = master_map_flash_region(flash->mst, flash->chip->name, base, size);
	if (addr == ERROR_PTR) {
		msg_perr("Could not map flash chip %s at 0x%0*" PRIxPTR ".\n",
			 flash->chip->name, PRIxPTR_WIDTH, base);
		return 1;
	}
	flash->physical_memory = base;
	flash->virtual_memory = (chipaddr)addr;

	/* FIXME: Special function registers normally live 4 MByte below flash space, but it might be somewhere
	 * completely different on some chips and programmers, or not mappable at all.
	 * Ignore these problems for now and always report success. */
	if (flash->chip->feature_bits & FEATURE_REGISTERMAP) {
		base = 0xffffffff - size - 0x400000 + 1;
		addr = master_map_flash_region(flash->mst, "flash chip registers", base, size);
		if (addr == ERROR_PTR) {
			msg_pdbg2("Could not map flash chip registers %s at 0x%0*" PRIxPTR ".\n",
				 flash->chip->name, PRIxPTR_WIDTH, base);
			return 0;
		}
		flash->physical_registers = base;
		flash->virtual_registers = (chipaddr)addr;
	}
	return 0;
}

/*
 * Return a string corresponding to the bustype parameter.
 * Memory is obtained with malloc() and must be freed with free() by the caller.
 */
char *flashbuses_to_text(enum chipbustype bustype)
{
	char *ret = calloc(1, 1);
	/*
	 * FIXME: Once all chipsets and flash chips have been updated, NONSPI
	 * will cease to exist and should be eliminated here as well.
	 */
	if (bustype == BUS_NONSPI) {
		ret = strcat_realloc(ret, "Non-SPI, ");
	} else {
		if (bustype & BUS_PARALLEL)
			ret = strcat_realloc(ret, "Parallel, ");
		if (bustype & BUS_LPC)
			ret = strcat_realloc(ret, "LPC, ");
		if (bustype & BUS_FWH)
			ret = strcat_realloc(ret, "FWH, ");
		if (bustype & BUS_SPI)
			ret = strcat_realloc(ret, "SPI, ");
		if (bustype & BUS_PROG)
			ret = strcat_realloc(ret, "Programmer-specific, ");
		if (bustype == BUS_NONE)
			ret = strcat_realloc(ret, "None, ");
	}
	/* Kill last comma. */
	ret[strlen(ret) - 2] = '\0';
	ret = realloc(ret, strlen(ret) + 1);
	return ret;
}

static int init_default_layout(struct flashctx *flash)
{
	/* Fill default layout covering the whole chip. */
	if (flashrom_layout_new(&flash->default_layout) ||
	    flashrom_layout_add_region(flash->default_layout,
			0, flash->chip->total_size * 1024 - 1, "complete flash") ||
	    flashrom_layout_include_region(flash->default_layout, "complete flash"))
	        return -1;
	return 0;
}

/* special unit-test hook */
write_func_t *g_test_write_injector;

static write_func_t *lookup_write_func_ptr(const struct flashchip *chip)
{
	switch (chip->write) {
		case WRITE_JEDEC: return &write_jedec;
		case WRITE_JEDEC1: return &write_jedec_1;
		case WRITE_OPAQUE: return &write_opaque;
		case SPI_CHIP_WRITE1: return &spi_chip_write_1;
		case SPI_CHIP_WRITE256: return &spi_chip_write_256;
		case SPI_WRITE_AAI: return &spi_aai_write;
		case SPI_WRITE_AT45DB: return &spi_write_at45db;
		case WRITE_28SF040: return &write_28sf040;
		case WRITE_82802AB: return &write_82802ab;
		case WRITE_EN29LV640B: return &write_en29lv640b;
		case EDI_CHIP_WRITE: return &edi_chip_write;
		case TEST_WRITE_INJECTOR: return g_test_write_injector;
	/* default: total function, 0 indicates no write function set.
	 * We explicitly do not want a default catch-all case in the switch
	 * to ensure unhandled enum's are compiler warnings.
	 */
		case NO_WRITE_FUNC: return NULL;
	};

	return NULL;
}

static int write_flash(struct flashctx *flash, const uint8_t *buf, unsigned int start, unsigned int len)
{
	write_func_t *write_func = lookup_write_func_ptr(flash->chip);
	return write_func(flash, buf, start, len);
}

typedef int (probe_func_t)(struct flashctx *flash);

static probe_func_t *lookup_probe_func_ptr(const struct flashchip *chip)
{
	switch (chip->probe) {
		case PROBE_JEDEC: return &probe_jedec;
		case PROBE_JEDEC_29GL: return &probe_jedec_29gl;
		case PROBE_OPAQUE: return &probe_opaque;
		case PROBE_EDI_KB9012: return &edi_probe_kb9012;
		case PROBE_AT82802AB: return &probe_82802ab;
		case PROBE_W29EE011: return &probe_w29ee011;
		case PROBE_EN29LV640B: return &probe_en29lv640b;
		case PROBE_SPI_AT25F: return &probe_spi_at25f;
		case PROBE_SPI_AT45DB: return &probe_spi_at45db;
		case PROBE_SPI_BIG_SPANSION: return &probe_spi_big_spansion;
		case PROBE_SPI_RDID: return &probe_spi_rdid;
		case PROBE_SPI_RDID4: return &probe_spi_rdid4;
		case PROBE_SPI_REMS: return &probe_spi_rems;
		case PROBE_SPI_RES1: return &probe_spi_res1;
		case PROBE_SPI_RES2: return &probe_spi_res2;
		case PROBE_SPI_SFDP: return &probe_spi_sfdp;
		case PROBE_SPI_ST95: return &probe_spi_st95;
		/* default: total function, 0 indicates no probe function set.
		 * We explicitly do not want a default catch-all case in the switch
		 * to ensure unhandled enum's are compiler warnings.
		 */
		case NO_PROBE_FUNC: return NULL;
	};

	return NULL;
}

int probe_flash(struct registered_master *mst, int startchip, struct flashctx *flash, int force, const char *const chip_to_probe)
{
	const struct flashchip *chip;
	enum chipbustype buses_common;
	char *tmp;

	for (chip = flashchips + startchip; chip && chip->name; chip++) {
		if (chip_to_probe && strcmp(chip->name, chip_to_probe) != 0)
			continue;
		buses_common = mst->buses_supported & chip->bustype;
		if (!buses_common)
			continue;
		/* Only probe for SPI25 chips by default. */
		if (chip->bustype == BUS_SPI && !chip_to_probe && chip->spi_cmd_set != SPI25)
			continue;
		msg_gdbg("Probing for %s %s, %d kB: ", chip->vendor, chip->name, chip->total_size);
		probe_func_t *probe_func = lookup_probe_func_ptr(chip);
		if (!probe_func && !force) {
			msg_gdbg("failed! flashrom has no probe function for this flash chip.\n");
			continue;
		}

		/* Start filling in the dynamic data. */
		flash->chip = calloc(1, sizeof(*flash->chip));
		if (!flash->chip) {
			msg_gerr("Out of memory!\n");
			return -1;
		}
		*flash->chip = *chip;
		flash->mst = mst;

		if (map_flash(flash) != 0)
			goto notfound;

		/* We handle a forced match like a real match, we just avoid probing. Note that probe_flash()
		 * is only called with force=1 after normal probing failed.
		 */
		if (force)
			break;

		if (probe_func == &probe_w29ee011)
			if (!w29ee011_can_override(flash->chip->name, chip_to_probe))
				goto notfound;

		if (probe_func(flash) != 1)
			goto notfound;

		/* If this is the first chip found, accept it.
		 * If this is not the first chip found, accept it only if it is
		 * a non-generic match. SFDP and CFI are generic matches.
		 * startchip==0 means this call to probe_flash() is the first
		 * one for this programmer interface (master) and thus no other chip has
		 * been found on this interface.
		 */
		if (startchip == 0 && flash->chip->model_id == SFDP_DEVICE_ID) {
			msg_cinfo("===\n"
				  "SFDP has autodetected a flash chip which is "
				  "not natively supported by flashrom yet.\n");
			if (count_usable_erasers(flash) == 0)
				msg_cinfo("The standard operations read and "
					  "verify should work, but to support "
					  "erase, write and all other "
					  "possible features");
			else
				msg_cinfo("All standard operations (read, "
					  "verify, erase and write) should "
					  "work, but to support all possible "
					  "features");

			msg_cinfo(" we need to add them manually.\n"
				  "You can help us by mailing us the output of the following command to "
				  "flashrom@flashrom.org:\n"
				  "'flashrom -VV [plus the -p/--programmer parameter]'\n"
				  "Thanks for your help!\n"
				  "===\n");
		}

		/* First flash chip detected on this bus. */
		if (startchip == 0)
			break;
		/* Not the first flash chip detected on this bus, but not a generic match either. */
		if ((flash->chip->model_id != GENERIC_DEVICE_ID) && (flash->chip->model_id != SFDP_DEVICE_ID))
			break;
		/* Not the first flash chip detected on this bus, and it's just a generic match. Ignore it. */
notfound:
		unmap_flash(flash);
		free(flash->chip);
		flash->chip = NULL;
	}

	if (!flash->chip)
		return -1;

	if (init_default_layout(flash) < 0)
		return -1;

	tmp = flashbuses_to_text(flash->chip->bustype);
	msg_cinfo("%s %s flash chip \"%s\" (%d kB, %s) ", force ? "Assuming" : "Found",
		  flash->chip->vendor, flash->chip->name, flash->chip->total_size, tmp);
	free(tmp);
	if (master_uses_physmap(mst))
		msg_cinfo("mapped at physical address 0x%0*" PRIxPTR ".\n",
			  PRIxPTR_WIDTH, flash->physical_memory);
	else
		msg_cinfo("on %s.\n", programmer->name);

	/* Flash registers may more likely not be mapped if the chip was forced.
	 * Lock info may be stored in registers, so avoid lock info printing. */
	if (!force)
		if (flash->chip->printlock)
			flash->chip->printlock(flash);

	/* Get out of the way for later runs. */
	unmap_flash(flash);

	/* Return position of matching chip. */
	return chip - flashchips;
}

/**
 * @brief Reads the included layout regions into a buffer.
 *
 * If there is no layout set in the given flash context, the whole chip will
 * be read.
 *
 * @param flashctx Flash context to be used.
 * @param buffer   Buffer of full chip size to read into.
 * @return 0 on success,
 *	   1 if any read fails.
 */
static int read_by_layout(struct flashctx *const flashctx, uint8_t *const buffer)
{
	const struct flashrom_layout *const layout = get_layout(flashctx);
	const struct romentry *entry = NULL;

	while ((entry = layout_next_included(layout, entry))) {
		const chipoff_t region_start	= entry->start;
		const chipsize_t region_len	= entry->end - entry->start + 1;

		if (read_flash(flashctx, buffer + region_start, region_start, region_len))
			return 1;
	}
	return 0;
}

/* Even if an error is found, the function will keep going and check the rest. */
static int selfcheck_eraseblocks(const struct flashchip *chip)
{
	int i, j, k;
	int ret = 0;
	unsigned int prev_eraseblock_count = chip->total_size * 1024;

	for (k = 0; k < NUM_ERASEFUNCTIONS; k++) {
		unsigned int done = 0;
		struct block_eraser eraser = chip->block_erasers[k];
		unsigned int curr_eraseblock_count = 0;

		for (i = 0; i < NUM_ERASEREGIONS; i++) {
			/* Blocks with zero size are bugs in flashchips.c. */
			if (eraser.eraseblocks[i].count &&
			    !eraser.eraseblocks[i].size) {
				msg_gerr("ERROR: Flash chip %s erase function "
					"%i region %i has size 0. Please report"
					" a bug at flashrom@flashrom.org\n",
					chip->name, k, i);
				ret = 1;
			}
			/* Blocks with zero count are bugs in flashchips.c. */
			if (!eraser.eraseblocks[i].count &&
			    eraser.eraseblocks[i].size) {
				msg_gerr("ERROR: Flash chip %s erase function "
					"%i region %i has count 0. Please report"
					" a bug at flashrom@flashrom.org\n",
					chip->name, k, i);
				ret = 1;
			}
			done += eraser.eraseblocks[i].count *
				eraser.eraseblocks[i].size;
			curr_eraseblock_count += eraser.eraseblocks[i].count;
		}
		/* Empty eraseblock definition with erase function.  */
		if (!done && eraser.block_erase)
			msg_gspew("Strange: Empty eraseblock definition with "
				  "non-empty erase function. Not an error.\n");
		if (!done)
			continue;
		if (done != chip->total_size * 1024) {
			msg_gerr("ERROR: Flash chip %s erase function %i "
				"region walking resulted in 0x%06x bytes total,"
				" expected 0x%06x bytes. Please report a bug at"
				" flashrom@flashrom.org\n", chip->name, k,
				done, chip->total_size * 1024);
			ret = 1;
		}
		if (!eraser.block_erase)
			continue;
		/* Check if there are identical erase functions for different
		 * layouts. That would imply "magic" erase functions. The
		 * easiest way to check this is with function pointers.
		 */
		for (j = k + 1; j < NUM_ERASEFUNCTIONS; j++) {
			if (eraser.block_erase ==
			    chip->block_erasers[j].block_erase) {
				msg_gerr("ERROR: Flash chip %s erase function "
					"%i and %i are identical. Please report"
					" a bug at flashrom@flashrom.org\n",
					chip->name, k, j);
				ret = 1;
			}
		}
		if(curr_eraseblock_count > prev_eraseblock_count)
		{
			msg_gerr("ERROR: Flash chip %s erase function %i is not "
					"in order. Please report a bug at flashrom@flashrom.org\n",
					chip->name, k);
			ret = 1;
		}
		prev_eraseblock_count = curr_eraseblock_count;
	}
	return ret;
}

typedef int (*erasefn_t)(struct flashctx *, unsigned int addr, unsigned int len);
/**
 * @private
 *
 * For read-erase-write, `curcontents` and `newcontents` shall point
 * to buffers of the chip's size. Both are supposed to be prefilled
 * with at least the included layout regions of the current flash
 * contents (`curcontents`) and the data to be written to the flash
 * (`newcontents`).
 *
 * For erase, `curcontents` and `newcontents` shall be NULL-pointers.
 *
 * The `chipoff_t` values are used internally by `walk_by_layout()`.
 */
struct walk_info {
	uint8_t *curcontents;
	const uint8_t *newcontents;
	chipoff_t region_start;
	chipoff_t region_end;
	chipoff_t erase_start;
	chipoff_t erase_end;
};
/* returns 0 on success, 1 to retry with another erase function, 2 for immediate abort */
typedef int (*per_blockfn_t)(struct flashctx *, const struct walk_info *, erasefn_t);

static int walk_eraseblocks(struct flashctx *const flashctx,
			    struct walk_info *const info,
			    const size_t erasefunction, const per_blockfn_t per_blockfn)
{
	int ret;
	size_t i, j;
	bool first = true;
	struct block_eraser *const eraser = &flashctx->chip->block_erasers[erasefunction];

	info->erase_start = 0;
	for (i = 0; i < NUM_ERASEREGIONS; ++i) {
		/* count==0 for all automatically initialized array
		   members so the loop below won't be executed for them. */
		for (j = 0; j < eraser->eraseblocks[i].count; ++j, info->erase_start = info->erase_end + 1) {
			info->erase_end = info->erase_start + eraser->eraseblocks[i].size - 1;

			/* Skip any eraseblock that is completely outside the current region. */
			if (info->erase_end < info->region_start)
				continue;
			if (info->region_end < info->erase_start)
				break;

			/* Print this for every block except the first one. */
			if (first)
				first = false;
			else
				msg_cdbg(", ");
			msg_cdbg("0x%06x-0x%06x:", info->erase_start, info->erase_end);

			erasefunc_t *erase_func = lookup_erase_func_ptr(eraser);
			ret = per_blockfn(flashctx, info, erase_func);
			if (ret)
				return ret;
		}
		if (info->region_end < info->erase_start)
			break;
	}
	msg_cdbg("\n");
	return 0;
}

static int walk_by_layout(struct flashctx *const flashctx, struct walk_info *const info,
			  const per_blockfn_t per_blockfn)
{
	const struct flashrom_layout *const layout = get_layout(flashctx);
	const struct romentry *entry = NULL;

	all_skipped = true;
	msg_cinfo("Erasing and writing flash chip... ");

	while ((entry = layout_next_included(layout, entry))) {
		info->region_start = entry->start;
		info->region_end   = entry->end;

		size_t j;
		int error = 1; /* retry as long as it's 1 */
		for (j = 0; j < NUM_ERASEFUNCTIONS; ++j) {
			if (j != 0)
				msg_cinfo("Looking for another erase function.\n");
			msg_cdbg("Trying erase function %zi... ", j);
			if (check_block_eraser(flashctx, j, 1))
				continue;

			error = walk_eraseblocks(flashctx, info, j, per_blockfn);
			if (error != 1)
				break;

			if (info->curcontents) {
				msg_cinfo("Reading current flash chip contents... ");
				if (read_by_layout(flashctx, info->curcontents)) {
					/* Now we are truly screwed. Read failed as well. */
					msg_cerr("Can't read anymore! Aborting.\n");
					/* We have no idea about the flash chip contents, so
					   retrying with another erase function is pointless. */
					error = 2;
					break;
				}
				msg_cinfo("done. ");
			}
		}
		if (error == 1)
			msg_cinfo("No usable erase functions left.\n");
		if (error) {
			msg_cerr("FAILED!\n");
			return 1;
		}
	}
	if (all_skipped)
		msg_cinfo("\nWarning: Chip content is identical to the requested image.\n");
	msg_cinfo("Erase/write done.\n");
	return 0;
}

static int erase_block(struct flashctx *const flashctx,
		       const struct walk_info *const info, const erasefn_t erasefn)
{
	const unsigned int erase_len = info->erase_end + 1 - info->erase_start;
	const bool region_unaligned = info->region_start > info->erase_start ||
				      info->erase_end > info->region_end;
	uint8_t *backup_contents = NULL, *erased_contents = NULL;
	int ret = 2;

	/*
	 * If the region is not erase-block aligned, merge current flash con-
	 * tents into a new buffer `backup_contents`.
	 */
	if (region_unaligned) {
		backup_contents = malloc(erase_len);
		erased_contents = malloc(erase_len);
		if (!backup_contents || !erased_contents) {
			msg_cerr("Out of memory!\n");
			ret = 1;
			goto _free_ret;
		}
		memset(backup_contents, ERASED_VALUE(flashctx), erase_len);
		memset(erased_contents, ERASED_VALUE(flashctx), erase_len);

		msg_cdbg("R");
		/* Merge data preceding the current region. */
		if (info->region_start > info->erase_start) {
			const chipoff_t start	= info->erase_start;
			const chipsize_t len	= info->region_start - info->erase_start;
			if (read_flash(flashctx, backup_contents, start, len)) {
				msg_cerr("Can't read! Aborting.\n");
				goto _free_ret;
			}
		}
		/* Merge data following the current region. */
		if (info->erase_end > info->region_end) {
			const chipoff_t start     = info->region_end + 1;
			const chipoff_t rel_start = start - info->erase_start; /* within this erase block */
			const chipsize_t len      = info->erase_end - info->region_end;
			if (read_flash(flashctx, backup_contents + rel_start, start, len)) {
				msg_cerr("Can't read! Aborting.\n");
				goto _free_ret;
			}
		}
	}

	ret = 1;
	all_skipped = false;

	msg_cdbg("E");
	if (erasefn(flashctx, info->erase_start, erase_len))
		goto _free_ret;
	if (check_erased_range(flashctx, info->erase_start, erase_len)) {
		msg_cerr("ERASE FAILED!\n");
		goto _free_ret;
	}

	if (region_unaligned) {
		unsigned int starthere = 0, lenhere = 0, writecount = 0;
		/* get_next_write() sets starthere to a new value after the call. */
		while ((lenhere = get_next_write(erased_contents + starthere, backup_contents + starthere,
						 erase_len - starthere, &starthere, flashctx->chip->gran))) {
			if (!writecount++)
				msg_cdbg("W");
			/* Needs the partial write function signature. */
			if (write_flash(flashctx, backup_contents + starthere,
						  info->erase_start + starthere, lenhere))
				goto _free_ret;
			starthere += lenhere;
		}
	}

	ret = 0;

_free_ret:
	free(erased_contents);
	free(backup_contents);
	return ret;
}

/**
 * @brief Erases the included layout regions.
 *
 * If there is no layout set in the given flash context, the whole chip will
 * be erased.
 *
 * @param flashctx Flash context to be used.
 * @return 0 on success,
 *	   1 if all available erase functions failed.
 */
static int erase_by_layout(struct flashctx *const flashctx)
{
	struct walk_info info = { 0 };
	return walk_by_layout(flashctx, &info, &erase_block);
}

static int read_erase_write_block(struct flashctx *const flashctx,
				  const struct walk_info *const info, const erasefn_t erasefn)
{
	const chipsize_t erase_len = info->erase_end + 1 - info->erase_start;
	const bool region_unaligned = info->region_start > info->erase_start ||
				      info->erase_end > info->region_end;
	const uint8_t *newcontents = NULL;
	int ret = 2;

	/*
	 * If the region is not erase-block aligned, merge current flash con-
	 * tents into `info->curcontents` and a new buffer `newc`. The former
	 * is necessary since we have no guarantee that the full erase block
	 * was already read into `info->curcontents`. For the latter a new
	 * buffer is used since `info->newcontents` might contain data for
	 * other unaligned regions that touch this erase block too.
	 */
	if (region_unaligned) {
		msg_cdbg("R");
		uint8_t *const newc = malloc(erase_len);
		if (!newc) {
			msg_cerr("Out of memory!\n");
			return 1;
		}
		memcpy(newc, info->newcontents + info->erase_start, erase_len);

		/* Merge data preceding the current region. */
		if (info->region_start > info->erase_start) {
			const chipoff_t start	= info->erase_start;
			const chipsize_t len	= info->region_start - info->erase_start;
			if (read_flash(flashctx, newc, start, len)) {
				msg_cerr("Can't read! Aborting.\n");
				goto _free_ret;
			}
			memcpy(info->curcontents + start, newc, len);
		}
		/* Merge data following the current region. */
		if (info->erase_end > info->region_end) {
			const chipoff_t start     = info->region_end + 1;
			const chipoff_t rel_start = start - info->erase_start; /* within this erase block */
			const chipsize_t len      = info->erase_end - info->region_end;
			if (read_flash(flashctx, newc + rel_start, start, len)) {
				msg_cerr("Can't read! Aborting.\n");
				goto _free_ret;
			}
			memcpy(info->curcontents + start, newc + rel_start, len);
		}

		newcontents = newc;
	} else {
		newcontents = info->newcontents + info->erase_start;
	}

	ret = 1;
	bool skipped = true;
	uint8_t *const curcontents = info->curcontents + info->erase_start;
	const uint8_t erased_value = ERASED_VALUE(flashctx);
	if (!(flashctx->chip->feature_bits & FEATURE_NO_ERASE) &&
			need_erase(curcontents, newcontents, erase_len, flashctx->chip->gran, erased_value)) {
		if (erase_block(flashctx, info, erasefn))
			goto _free_ret;
		/* Erase was successful. Adjust curcontents. */
		memset(curcontents, erased_value, erase_len);
		skipped = false;
	}

	unsigned int starthere = 0, lenhere = 0, writecount = 0;
	/* get_next_write() sets starthere to a new value after the call. */
	while ((lenhere = get_next_write(curcontents + starthere, newcontents + starthere,
					 erase_len - starthere, &starthere, flashctx->chip->gran))) {
		if (!writecount++)
			msg_cdbg("W");
		/* Needs the partial write function signature. */
		if (write_flash(flashctx, newcontents + starthere,
					  info->erase_start + starthere, lenhere))
			goto _free_ret;
		starthere += lenhere;
		skipped = false;
	}
	if (skipped)
		msg_cdbg("S");
	else
		all_skipped = false;

	/* Update curcontents, other regions with overlapping erase blocks
	   might rely on this. */
	memcpy(curcontents, newcontents, erase_len);
	ret = 0;

_free_ret:
	if (region_unaligned)
		free((void *)newcontents);
	return ret;
}

/**
 * @brief Writes the included layout regions from a given image.
 *
 * If there is no layout set in the given flash context, the whole image
 * will be written.
 *
 * @param flashctx    Flash context to be used.
 * @param curcontents A buffer of full chip size with current chip contents of included regions.
 * @param newcontents The new image to be written.
 * @return 0 on success,
 *	   1 if anything has gone wrong.
 */
static int write_by_layout(struct flashctx *const flashctx,
			   void *const curcontents, const void *const newcontents)
{
	struct walk_info info;
	info.curcontents = curcontents;
	info.newcontents = newcontents;
	return walk_by_layout(flashctx, &info, read_erase_write_block);
}

/**
 * @brief Compares the included layout regions with content from a buffer.
 *
 * If there is no layout set in the given flash context, the whole chip's
 * contents will be compared.
 *
 * @param flashctx    Flash context to be used.
 * @param layout      Flash layout information.
 * @param curcontents A buffer of full chip size to read current chip contents into.
 * @param newcontents The new image to compare to.
 * @return 0 on success,
 *	   1 if reading failed,
 *	   3 if the contents don't match.
 */
static int verify_by_layout(
		struct flashctx *const flashctx,
		const struct flashrom_layout *const layout,
		void *const curcontents, const uint8_t *const newcontents)
{
	const struct romentry *entry = NULL;

	while ((entry = layout_next_included(layout, entry))) {
		const chipoff_t region_start	= entry->start;
		const chipsize_t region_len	= entry->end - entry->start + 1;

		if (read_flash(flashctx, curcontents + region_start, region_start, region_len))
			return 1;
		if (compare_range(newcontents + region_start, curcontents + region_start,
				  region_start, region_len))
			return 3;
	}
	return 0;
}

static bool is_internal_programmer()
{
#if CONFIG_INTERNAL == 1
	return programmer == &programmer_internal;
#else
	return false;
#endif
}

static void nonfatal_help_message(void)
{
	msg_gerr("Good, writing to the flash chip apparently didn't do anything.\n");
	if (is_internal_programmer())
		msg_gerr("This means we have to add special support for your board, programmer or flash\n"
			 "chip. Please report this to the mailing list at flashrom@flashrom.org or on\n"
			 "IRC (see https://www.flashrom.org/Contact for details), thanks!\n"
			 "-------------------------------------------------------------------------------\n"
			 "You may now reboot or simply leave the machine running.\n");
	else
		msg_gerr("Please check the connections (especially those to write protection pins) between\n"
			 "the programmer and the flash chip. If you think the error is caused by flashrom\n"
			 "please report this to the mailing list at flashrom@flashrom.org or on IRC (see\n"
			 "https://www.flashrom.org/Contact for details), thanks!\n");
}

void emergency_help_message(void)
{
	msg_gerr("Your flash chip is in an unknown state.\n");
	if (is_internal_programmer())
		msg_gerr("Get help on IRC (see https://www.flashrom.org/Contact) or mail\n"
			"flashrom@flashrom.org with the subject \"FAILED: <your board name>\"!"
			"-------------------------------------------------------------------------------\n"
			"DO NOT REBOOT OR POWEROFF!\n");
	else
		msg_gerr("Please report this to the mailing list at flashrom@flashrom.org or\n"
			 "on IRC (see https://www.flashrom.org/Contact for details), thanks!\n");
}

void list_programmers_linebreak(int startcol, int cols, int paren)
{
	const char *pname;
	int pnamelen;
	int remaining = 0, firstline = 1;
	size_t p;
	int i;

	for (p = 0; p < programmer_table_size; p++) {
		pname = programmer_table[p]->name;
		pnamelen = strlen(pname);
		if (remaining - pnamelen - 2 < 0) {
			if (firstline)
				firstline = 0;
			else
				msg_ginfo("\n");
			for (i = 0; i < startcol; i++)
				msg_ginfo(" ");
			remaining = cols - startcol;
		} else {
			msg_ginfo(" ");
			remaining--;
		}
		if (paren && (p == 0)) {
			msg_ginfo("(");
			remaining--;
		}
		msg_ginfo("%s", pname);
		remaining -= pnamelen;
		if (p < programmer_table_size - 1) {
			msg_ginfo(",");
			remaining--;
		} else {
			if (paren)
				msg_ginfo(")");
		}
	}
}

int selfcheck(void)
{
	unsigned int i;
	int ret = 0;

	for (i = 0; i < programmer_table_size; i++) {
		const struct programmer_entry *const p = programmer_table[i];
		if (p == NULL) {
			msg_gerr("Programmer with index %d is NULL instead of a valid pointer!\n", i);
			ret = 1;
			continue;
		}
		if (p->name == NULL) {
			msg_gerr("All programmers need a valid name, but the one with index %d does not!\n", i);
			ret = 1;
			/* This might hide other problems with this programmer, but allows for better error
			 * messages below without jumping through hoops. */
			continue;
		}
		switch (p->type) {
		case USB:
		case PCI:
		case OTHER:
			if (p->devs.note == NULL) {
				if (strcmp("internal", p->name) == 0)
					break; /* This one has its device list stored separately. */
				msg_gerr("Programmer %s has neither a device list nor a textual description!\n",
					 p->name);
				ret = 1;
			}
			break;
		default:
			msg_gerr("Programmer %s does not have a valid type set!\n", p->name);
			ret = 1;
			break;
		}
		if (p->init == NULL) {
			msg_gerr("Programmer %s does not have a valid init function!\n", p->name);
			ret = 1;
		}
	}

	/* It would be favorable if we could check for the correct layout (especially termination) of various
	 * constant arrays: flashchips, chipset_enables, board_matches, boards_known, laptops_known.
	 * They are all defined as externs in this compilation unit so we don't know their sizes which vary
	 * depending on compiler flags, e.g. the target architecture, and can sometimes be 0.
	 * For 'flashchips' we export the size explicitly to work around this and to be able to implement the
	 * checks below. */
	if (flashchips_size <= 1 || flashchips[flashchips_size - 1].name != NULL) {
		msg_gerr("Flashchips table miscompilation!\n");
		ret = 1;
	} else {
		for (i = 0; i < flashchips_size - 1; i++) {
			const struct flashchip *chip = &flashchips[i];
			if (chip->vendor == NULL || chip->name == NULL || chip->bustype == BUS_NONE) {
				ret = 1;
				msg_gerr("ERROR: Some field of flash chip #%d (%s) is misconfigured.\n"
					 "Please report a bug at flashrom@flashrom.org\n", i,
					 chip->name == NULL ? "unnamed" : chip->name);
			}
			if (selfcheck_eraseblocks(chip)) {
				ret = 1;
			}
		}
	}

#if CONFIG_INTERNAL == 1
	ret |= selfcheck_board_enables();
#endif

	/* TODO: implement similar sanity checks for other arrays where deemed necessary. */
	return ret;
}

/* FIXME: This function signature needs to be improved once prepare_flash_access()
 * has a better function signature.
 */
static int chip_safety_check(const struct flashctx *flash, int force,
			     int read_it, int write_it, int erase_it, int verify_it)
{
	const struct flashchip *chip = flash->chip;

	if (!programmer_may_write && (write_it || erase_it)) {
		msg_perr("Write/erase is not working yet on your programmer in "
			 "its current configuration.\n");
		/* --force is the wrong approach, but it's the best we can do
		 * until the generic programmer parameter parser is merged.
		 */
		if (!force)
			return 1;
		msg_cerr("Continuing anyway.\n");
	}

	if (read_it || erase_it || write_it || verify_it) {
		/* Everything needs read. */
		if (chip->tested.read == BAD) {
			msg_cerr("Read is not working on this chip. ");
			if (!force)
				return 1;
			msg_cerr("Continuing anyway.\n");
		}
		if (!lookup_read_func_ptr(chip)) {
			msg_cerr("flashrom has no read function for this "
				 "flash chip.\n");
			return 1;
		}
	}
	if (erase_it || write_it) {
		/* Write needs erase. */
		if (chip->tested.erase == NA) {
			msg_cerr("Erase is not possible on this chip.\n");
			return 1;
		}
		if (chip->tested.erase == BAD) {
			msg_cerr("Erase is not working on this chip. ");
			if (!force)
				return 1;
			msg_cerr("Continuing anyway.\n");
		}
		if(count_usable_erasers(flash) == 0) {
			msg_cerr("flashrom has no erase function for this "
				 "flash chip.\n");
			return 1;
		}
	}
	if (write_it) {
		if (chip->tested.write == NA) {
			msg_cerr("Write is not possible on this chip.\n");
			return 1;
		}
		if (chip->tested.write == BAD) {
			msg_cerr("Write is not working on this chip. ");
			if (!force)
				return 1;
			msg_cerr("Continuing anyway.\n");
		}
		if (!lookup_write_func_ptr(chip)) {
			msg_cerr("flashrom has no write function for this "
				 "flash chip.\n");
			return 1;
		}
	}
	return 0;
}

int prepare_flash_access(struct flashctx *const flash,
			 const bool read_it, const bool write_it,
			 const bool erase_it, const bool verify_it)
{
	if (chip_safety_check(flash, flash->flags.force, read_it, write_it, erase_it, verify_it)) {
		msg_cerr("Aborting.\n");
		return 1;
	}

	if (layout_sanity_checks(flash)) {
		msg_cerr("Requested regions can not be handled. Aborting.\n");
		return 1;
	}

	if (map_flash(flash) != 0)
		return 1;

	/* Initialize chip_restore_fn_count before chip unlock calls. */
	flash->chip_restore_fn_count = 0;

	/* Given the existence of read locks, we want to unlock for read,
	   erase and write. */
	if (flash->chip->unlock)
		flash->chip->unlock(flash);

	flash->address_high_byte = -1;
	flash->in_4ba_mode = false;

	/* Be careful about 4BA chips and broken masters */
	if (flash->chip->total_size > 16 * 1024 && spi_master_no_4ba_modes(flash)) {
		/* If we can't use native instructions, bail out */
		if ((flash->chip->feature_bits & FEATURE_4BA_NATIVE) != FEATURE_4BA_NATIVE
		    || !spi_master_4ba(flash)) {
			msg_cerr("Programmer doesn't support this chip. Aborting.\n");
			return 1;
		}
	}

	/* Enable/disable 4-byte addressing mode if flash chip supports it */
	if (flash->chip->feature_bits & (FEATURE_4BA_ENTER | FEATURE_4BA_ENTER_WREN | FEATURE_4BA_ENTER_EAR7)) {
		int ret;
		if (spi_master_4ba(flash))
			ret = spi_enter_4ba(flash);
		else
			ret = spi_exit_4ba(flash);
		if (ret) {
			msg_cerr("Failed to set correct 4BA mode! Aborting.\n");
			return 1;
		}
	}

	return 0;
}

void finalize_flash_access(struct flashctx *const flash)
{
	deregister_chip_restore(flash);
	unmap_flash(flash);
}

int flashrom_flash_erase(struct flashctx *const flashctx)
{
	if (prepare_flash_access(flashctx, false, false, true, false))
		return 1;

	const int ret = erase_by_layout(flashctx);

	finalize_flash_access(flashctx);

	return ret;
}

int flashrom_image_read(struct flashctx *const flashctx, void *const buffer, const size_t buffer_len)
{
	const size_t flash_size = flashctx->chip->total_size * 1024;

	if (flash_size > buffer_len)
		return 2;

	if (prepare_flash_access(flashctx, true, false, false, false))
		return 1;

	msg_cinfo("Reading flash... ");

	int ret = 1;
	if (read_by_layout(flashctx, buffer)) {
		msg_cerr("Read operation failed!\n");
		msg_cinfo("FAILED.\n");
		goto _finalize_ret;
	}
	msg_cinfo("done.\n");
	ret = 0;

_finalize_ret:
	finalize_flash_access(flashctx);
	return ret;
}

static void combine_image_by_layout(const struct flashctx *const flashctx,
				    uint8_t *const newcontents, const uint8_t *const oldcontents)
{
	const struct flashrom_layout *const layout = get_layout(flashctx);
	const struct romentry *included;
	chipoff_t start = 0;

	while ((included = layout_next_included_region(layout, start))) {
		if (included->start > start) {
			/* copy everything up to the start of this included region */
			memcpy(newcontents + start, oldcontents + start, included->start - start);
		}
		/* skip this included region */
		start = included->end + 1;
		if (start == 0)
			return;
	}

	/* copy the rest of the chip */
	const chipsize_t copy_len = flashctx->chip->total_size * 1024 - start;
	memcpy(newcontents + start, oldcontents + start, copy_len);
}

int flashrom_image_write(struct flashctx *const flashctx, void *const buffer, const size_t buffer_len,
                         const void *const refbuffer)
{
	const size_t flash_size = flashctx->chip->total_size * 1024;
	const bool verify_all = flashctx->flags.verify_whole_chip;
	const bool verify = flashctx->flags.verify_after_write;
	const struct flashrom_layout *const verify_layout =
		verify_all ? get_default_layout(flashctx) : get_layout(flashctx);

	if (buffer_len != flash_size)
		return 4;

	int ret = 1;

	uint8_t *const newcontents = buffer;
	const uint8_t *const refcontents = refbuffer;
	uint8_t *const curcontents = malloc(flash_size);
	uint8_t *oldcontents = NULL;
	if (verify_all)
		oldcontents = malloc(flash_size);
	if (!curcontents || (verify_all && !oldcontents)) {
		msg_gerr("Out of memory!\n");
		goto _free_ret;
	}

#if CONFIG_INTERNAL == 1
	if (is_internal_programmer() && cb_check_image(newcontents, flash_size) < 0) {
		if (flashctx->flags.force_boardmismatch) {
			msg_pinfo("Proceeding anyway because user forced us to.\n");
		} else {
			msg_perr("Aborting. You can override this with "
				 "-p internal:boardmismatch=force.\n");
			goto _free_ret;
		}
	}
#endif

	if (prepare_flash_access(flashctx, false, true, false, verify))
		goto _free_ret;

	/* If given, assume flash chip contains same data as `refcontents`. */
	if (refcontents) {
		msg_cinfo("Assuming old flash chip contents as ref-file...\n");
		memcpy(curcontents, refcontents, flash_size);
		if (oldcontents)
			memcpy(oldcontents, refcontents, flash_size);
	} else {
		/*
		 * Read the whole chip to be able to check whether regions need to be
		 * erased and to give better diagnostics in case write fails.
		 * The alternative is to read only the regions which are to be
		 * preserved, but in that case we might perform unneeded erase which
		 * takes time as well.
		 */
		msg_cinfo("Reading old flash chip contents... ");
		if (verify_all) {
			if (read_flash(flashctx, oldcontents, 0, flash_size)) {
				msg_cinfo("FAILED.\n");
				goto _finalize_ret;
			}
			memcpy(curcontents, oldcontents, flash_size);
		} else {
			if (read_by_layout(flashctx, curcontents)) {
				msg_cinfo("FAILED.\n");
				goto _finalize_ret;
			}
		}
		msg_cinfo("done.\n");
	}

	if (write_by_layout(flashctx, curcontents, newcontents)) {
		msg_cerr("Uh oh. Erase/write failed. ");
		ret = 2;
		if (verify_all) {
			msg_cerr("Checking if anything has changed.\n");
			msg_cinfo("Reading current flash chip contents... ");
			if (!read_flash(flashctx, curcontents, 0, flash_size)) {
				msg_cinfo("done.\n");
				if (!memcmp(oldcontents, curcontents, flash_size)) {
					nonfatal_help_message();
					goto _finalize_ret;
				}
				msg_cerr("Apparently at least some data has changed.\n");
			} else
				msg_cerr("Can't even read anymore!\n");
			emergency_help_message();
			goto _finalize_ret;
		} else {
			msg_cerr("\n");
		}
		emergency_help_message();
		goto _finalize_ret;
	}

	/* Verify only if we actually changed something. */
	if (verify && !all_skipped) {
		msg_cinfo("Verifying flash... ");

		/* Work around chips which need some time to calm down. */
		programmer_delay(flashctx, 1000*1000);

		if (verify_all)
			combine_image_by_layout(flashctx, newcontents, oldcontents);
		ret = verify_by_layout(flashctx, verify_layout, curcontents, newcontents);
		/* If we tried to write, and verification now fails, we
		   might have an emergency situation. */
		if (ret)
			emergency_help_message();
		else
			msg_cinfo("VERIFIED.\n");
	} else {
		/* We didn't change anything. */
		ret = 0;
	}

_finalize_ret:
	finalize_flash_access(flashctx);
_free_ret:
	free(oldcontents);
	free(curcontents);
	return ret;
}

int flashrom_image_verify(struct flashctx *const flashctx, const void *const buffer, const size_t buffer_len)
{
	const struct flashrom_layout *const layout = get_layout(flashctx);
	const size_t flash_size = flashctx->chip->total_size * 1024;

	if (buffer_len != flash_size)
		return 2;

	const uint8_t *const newcontents = buffer;
	uint8_t *const curcontents = malloc(flash_size);
	if (!curcontents) {
		msg_gerr("Out of memory!\n");
		return 1;
	}

	int ret = 1;

	if (prepare_flash_access(flashctx, false, false, false, true))
		goto _free_ret;

	msg_cinfo("Verifying flash... ");
	ret = verify_by_layout(flashctx, layout, curcontents, newcontents);
	if (!ret)
		msg_cinfo("VERIFIED.\n");

	finalize_flash_access(flashctx);
_free_ret:
	free(curcontents);
	return ret;
}